Antibiotic Sales Doesn’t Make Case for Public Health Threat

This week the Food and Drug Administration (FDA) released some valuable reports about antimicrobial sales in livestock, according to a blog posted by Scott Hurd, DVM, Iowa State University.

The links from FDA noted below explain from where the data are derived and offer some good thoughts about interpretation. I will highlight a few points.

1. There appears to have been an increase in antibiotic sales from 2010 to 2011. If you remove ionophores, which are never used in humans, nor are their cousins, there was actually a 0.01% decrease. Additionally, if you compare those data to meat production, which increased by at least 0.2%, producers have apparently reduced antimicrobial use quite a bit.

FDA notes this is only the third year these data have been reported, so don’t get too excited about slight changes in the volumes. They say it more professionally of course (see below). Note also that since these are sales data, it could easily reflect changes in inventory on hand. NOTE, they do not reflect actual usage in animals!!

“It is not unexpected to see transient increases or decreases in sales of certain drugs in a given year due to various factors (e.g., occurrence of disease outbreaks, fluctuations in animal populations). Therefore, given that only three years of sales data have been compiled so far, it is difficult at this time to draw conclusions about whether any changes in sales data represent meaningful trends in overall volume of sales or the resulting effect on antimicrobial resistance.”

2. FDA is very clear these data cannot be compared to other sources on animal and human use. Some folks try to make those comparisons. FDA says, “Don’t go there!” – again, more professionally of course.

“The Section 105 summary report is not directly comparable to other previously reported estimates of antimicrobial drug sales or distribution. The Section 105 summary report includes data on the quantity of antimicrobial drugs sold or distributed for use in all food-producing animal species for all purposes, both therapeutic and non-therapeutic, and includes all dosage forms. Previously reported estimates included different categories of antimicrobials and used different sources of information and thus cannot be directly compared to the Section 105 summary report.”

How do the data collected for animal use compare to the amount of antimicrobial drugs used in humans?

“It is very difficult to compare the animal and human reports in any meaningful way. Before making comparisons between human and animal sales and distribution data, there are a number of differences in the circumstances of use of antibacterial drugs in human and veterinary medicine that must be carefully considered.”

“Antimicrobial drug data collection helps FDA evaluate antimicrobial resistance trends. The data also help the agency in its analyses of other issues that may arise relating to the safety and effectiveness of antimicrobial drugs approved for use in food-producing animals.”

However, as we point out in our recent Food and Drug Law Institute (FDLI) paper aimed toward the lawyers, data on usage is only marginally informative. Some comparison or outcome measure is also needed: “Conclusions based on one half of the equation (sales or usage data only) cannot be substantiated.”

In other words, if on-farm antimicrobial use does not increase public health harm due to treatment failures from resistant infections, then sales data are not that interesting. It is true that treatment failures occur in human hospitals, but those are usually from bacteria and resistance genomes not closely related to the farm, e.g staphylococcus and enterococcus, not salmonella and campylobacter.

Therefore, the removal of on-farm antimicrobials may make little to no improvement in public health, as discovered in Denmark. More on that later.